The present invention relates to a transmission between a driving primary shaft and an outlet shaft, such as the wheel drive shaft of a self-propelled machine.
The invention relates more particularly to a transmission of the type comprising at least one housing within which there are housed at least in part: a stepdown mechanism comprising a driving member, such as a wormscrew, meshing with a driven rotary member, such as a gearwheel that is mounted free to rotate on the outlet shaft; two clutch mechanisms, one of the mechanisms being progressive and the other mechanism being non-progressive with a movable dog, whereby the driven rotary member is suitable for being coupled/decoupled with or from the outlet shaft; and a clutch control device comprising both first clutch control means for driving the movable dog of the non-progressive clutch mechanism in axial movement along the outlet shaft between two extreme positions, said first clutch control means being capable of being actuated from outside the housing, and also second clutch control means mounted on the outlet shaft to move under the action of the movable dog moving axially in the clutching direction, by bearing contact against said movable dog, between firstly an active position in which said second clutch control means are interposed between the movable dog and the progressive clutch mechanism and form a member for transmitting axial movement from the movable dog to the progressive clutch mechanism in order to pass the progressive clutch mechanism from a declutched position to a clutched position, and secondly an inactive or retracted position in which the movable dog is suitable for passing from an unclutched position to the clutched position of the non-progressive clutch mechanism.
Such transmissions are well known to those skilled in this art, as illustrated by patent GB-2 030 660. Such transmissions are inexpensive compared with a transmission having progressive clutch mechanisms exclusively, while nevertheless conserving the absence of jolting and conserving the progressive nature of a progressive clutch.
Nevertheless, until now, the second clutch control means have been made in a manner that is complex and lacking in reliability.